Effect of motion path of downburst on wind-induced conductor swing in transmission line

Wenjuan Lou,Jiawei Wang,Yong Chen,Zhongbin Lv,Ming Lu Xu 한국풍공학회 2016 Wind and Structures, An International Journal (WAS Vol.23 No.3

In recent years, the frequency and duration of supply interruption in electric power transmission system due to flashover increase yearly in China. Flashover is usually associated with inadequate electric clearance and often takes place in extreme weathers, such as downbursts, typhoons and hurricanes. The present study focuses on the wind-induced oscillation of conductor during the process when a downburst is passing by or across a specified transmission line. Based on a revised analytical model recently developed for stationary downburst, transient three-dimensional wind fields of moving downbursts are successfully simulated. In the simulations, the downbursts travel along various motion paths according to the certain initial locations and directions of motion assumed in advance. Then, an eight-span section, extracted from a practical 500 kV ultra-high-voltage transmission line, is chosen. After performing a non-linear transient analysis, the transient displacements of the conductors could be obtained. Also, an extensive study on suspension insulator strings` rotation angles is conducted, and the electric clearances at different strings could be compared directly. The results show that both the variation trends of the transient responses and the corresponding peak values vary seriously with the motion paths of downburst. Accordingly, the location of the specified string, which is in the most disadvantageous situation along the studied line section, is picked out. And a representative motion path is concluded for reference in the calculation of each string`s oscillation for the precaution of wind-induced flashover under downburst.

Transonic characteristics for AGARD Wing 445.6 by numerical simulation

Wenjuan Ye,Youngshin Lee,Jinhai Lan 한국추진공학회 2010 한국추진공학회 학술대회논문집 Vol.2010 No.5

The supersonic speeds slowing down by shock waves is a common problem during the transonic region. So how to study the status of shock on the surface of airplane and wings is crucial adjective during transonic region. However, the theoretical and computational transonic flow problems were very hard. This paper introduced using Navier-Stokes Schemes to study characteristics of AGARD Wing 445.6 by ANSYS CFX in transonic region. From simulations results, as the Mach number increases, shock waves appear in the flowfield, getting stronger as the speed increases, these shock waves will lead to a rapid increase in drag.

The Efect of ADRC on Vehicle Braking Performance

Wenjuan Li,Qi Zhang,Yuan Zhang 대한전기학회 2020 Journal of Electrical Engineering & Technology Vol.15 No.2

The active disturbance rejection control (ADRC) was proposed as a control strategy for anti-lock braking system (ABS) to improve the braking performance. A real-time simulation model was developed after analyzing the brake force during vehicle braking and the ADRC principle. This experimental real-time simulation platform was developed based on xPC Target. This ABS study was conducted on a dry concrete pavement, and the braking performance indices were analyzed under the ADRC and the bang–bang control. The results suggest that the braking performance is more superior with ADRC than the bang–bang control because the braking time and braking distance were reduced. The xPC Target is a less-costly and practical method for real-time simulation.

Wind field generation for performance-based structural design of transmission lines in a mountainous area

Wenjuan Lou,Hang Bai,Mingfeng Huang,Zhiyong Duan,Rong Bian 한국풍공학회 2020 Wind and Structures, An International Journal (WAS Vol.31 No.2

The first step of performance-based design for transmission lines is the determination of wind fields as well as wind loads, which are largely depending on local wind climate and the surrounding terrain. Wind fields in a mountainous area are very different with that in a flat terrain. This paper firstly investigated both mean and fluctuating wind characteristics of a typical mountainous wind field by wind tunnel tests and computational fluid dynamics (CFD). The speedup effects of mean wind and specific turbulence properties, i.e., turbulence intensity, power spectral density (PSD) and coherence function, are highlighted. Then a hybrid simulation framework for generating three dimensional (3D) wind velocity field in the mountainous area was proposed by combining the CFD and proper orthogonal decomposition (POD) method given the properties of the target turbulence field. Finally, a practical 220 kV transmission line was employed to demonstrate the effectiveness of the proposed wind field generation framework and its role in the performance-based design. It was found that the terrain-induce turbulence effects dominate the performance-based structural design of transmission lines running through the mountainous area.

Analytical Solutions of Deformation of Uplift Belled Group Piles considering Reinforcement Effect

Wenjuan Yao,Lu Xiao 대한토목학회 2019 KSCE JOURNAL OF CIVIL ENGINEERING Vol.23 No.3

Up to now, the design method of uplift piles have still imitated the design of compressive piles, which results in that computation design theory is far behind of the engineering practice. As the interaction of piles has been very prominent and important in the deformation of pile groups, the deformation of the group piles has become the urgent issues in engineering applications. Based on the theory of elastic mechanics and principle of pile load transfer, it is derived that the nonlinear analytical expressions of deformation of uplift belled group piles considering reinforcement effect, and the specific calculation steps are given. The validity of the analytical method is verified through the comparison of the pictures, which consist of the calculated data of the analytical solution, the measured date of the model test and the results of finite element analysis. The results unveils that properties of soil, the expanded body of pile and the length of pile has impact on the deformation of uplift belled group piles considering the reinforcement effect significantly. With the increasing of elastic modulus of soil, the expanded body of pile and the length of pile, the uplift deformation of uplift belled group piles is reduced.

Stability analysis of bimodular pin-ended slender rod

Wenjuan Yao,Jianwei Ma,Baolin Hu 국제구조공학회 2011 Structural Engineering and Mechanics, An Int'l Jou Vol.40 No.4

Many novel materials, developed in recent years, have obvious properties with different modulus of elasticity in tension and compression. The ratio of their tensile modulus to compressive modulus is as high as five times. Nowadays, it has become a new trend to study the mechanical properties of these bimodular materials. At the present stage, there are extensive studies related to the strength analysis of bimodular structures, but the investigation of the buckling stability problem of bimodular rods seems to cover new ground. In this article, a semi-analytical method is proposed to acquire the buckling critical load of bimodular slender rod. By introducing non-dimensional parameters, the position of neutral axis of the bimodular rod in the critical state can be determined. Then by combining the phased integration method, the deflection differential equation of bimodular pin-ended slender rod is deduced. In addition, the buckling critical load is obtained by solving this equation. An example, which is conducted by comparing the calculation results between the three of the methods including the laboratory tests, numerical simulation method and the method we developed here, shows that the method proposed in the present work is reliable to use. Furthermore, the influence of bimodular characteristics on the stability is discussed and analyzed.

A note on the first order commutator $\mathcal{C}_2$

Wenjuan Li,Suying Liu 대한수학회 2019 대한수학회보 Vol.56 No.4

This paper gives a counterexample to show that the first order commutator $\mathcal {C}_2$ is not bounded from $H^{1}(\mathbb{R})\times H^{1}(\mathbb{R})$ into $L^{1/2}(\mathbb{R})$. Then we introduce the atomic definition of abstract weighted Hardy spaces $H_{ato,\omega}^{1}(\mathbb{R})$ and study its properties. At last, we prove that $\mathcal {C}_2$ maps $H_{ato,w}^{1}(\mathbb{R})\times H^{1}_{ato,w}(\mathbb{R})$ into $L^{1/2}_{\omega}(\mathbb{R})$.

Preparation of Functionalized Magnetic Silica Nanospheres for the Cellulase Immobilization

Wenjuan Zhang,Jianhui Qiu,Limin Zang,Eiichi Sakai,Huixia Feng 성균관대학교(자연과학캠퍼스) 성균나노과학기술원 2015 NANO Vol.10 No.1

Cellulase was immobilized on functionalized magnetic silica nanospheres using glutaraldehyde as a cross-linking agent. The morphologies, structures and magnetic properties of this immobilized cellulase were characterized by transmission electron microscopy, Fourier transform infrared spectroscopy, thermogravimetric analysis, differential thermal analysis and vibrating sample magnetometry. The properties of immobilized cellulase were investigated, including the amount of immobilized cellulase and its relative activity, stability and reusability. The results indicated that immobilized cellulase exhibited better resistance to high temperature and pH inactivation in comparison to free cellulase. Moreover, immobilized cellulase with and without cross-linking agent were investigated and the former had greater amount of immobilized cellulase and better operational stability. The amount of immobilized cellulase with the cross-linking agent was 92 mg/g support. Furthermore, the activity of the immobilized cellulase was still 85.5% of the initial activity after 10 continuous uses, demonstrating the potential of this immobilized cellulase for large-scale biofuel production.

Nonlinear large deflection buckling analysis of compression rod with different moduli

Wenjuan Yao,Jianwei Ma,Jinling Gao,Yuanzhong Qiu 국제구조공학회 2015 Structural Engineering and Mechanics, An Int'l Jou Vol.54 No.5

Many novel materials exhibit a property of different elastic moduli in tension and compression. One such material is graphene, a wonder material, which has the highest strength yet measured. Investigations on buckling problems for structures with different moduli are scarce. To address this new problem, firstly, the nondimensional expression of the relation between offset of neutral axis and deflection curve is derived based on the phased integration method, and then using the energy method, load-deflection relation of the rod is determined; Secondly, based on the improved constitutive model for different moduli, large deformation finite element formulations are developed and combined with the arc-length method, finite element iterative program for rods with different moduli is established to obtain buckling critical loads; Thirdly, material mechanical properties tests of graphite, which is the raw material of graphene, are performed to measure the tensile and compressive elastic moduli, moreover, buckling tests are also conducted to investigate the buckling behavior of this kind of graphite rod. By comparing the calculation results of the energy method and finite element method with those of laboratory tests, the analytical model and finite element numerical model are demonstrated to be accurate and reliable. The results show that it may lead to unsafe results if the classic theory was still adopted to determine the buckling loads of those rods composed of a material having different moduli. The proposed models could provide a novel approach for further investigation of non-linear mechanical behavior for other structures with different moduli.

Deformable Surface 3D Reconstruction from a Single Image by Linear Programming

( Wenjuan Ma ),( Shusen Sun ) 한국인터넷정보학회 2017 KSII Transactions on Internet and Information Syst Vol.11 No.6

We present a method for 3D shape reconstruction of inextensible deformable surfaces from a single image. The key of our approach is to represent the surface as a 3D triangulated mesh and formulate the reconstruction problem as a sequence of Linear Programming (LP) problems. The LP problem consists of data constraints which are 3D-to-2D keypoint correspondences and shape constraints which are designed to retain original lengths of mesh edges. We use a closed-form method to generate an initial structure, then refine this structure by solving the LP problem iteratively. Compared with previous methods, ours neither involves smoothness constraints nor temporal consistency, which enables us to recover shapes of surfaces with various deformations from a single image. The robustness and accuracy of our approach are evaluated quantitatively on synthetic data and qualitatively on real data.